John Spurgin

Dr. John Spurgin, M.D.

Inventor

Spurgin's Bridge

'NEW PLAN OF BRIDGE-BUILDING. A bridge has just been constructed the Chain Cable Works, Brown, Lenox, & Co., near Cardiff, according to Dr. Spurgin's patent, of a very novel description. A scientific correspondent of the Advertiser describes it as follows, and the small diagram may, perhaps, assist the reader in forming an idea of it:-

"The bridge is intended to cross the Motagua river in the new colony of Vera Paz, (and effects the first road communication direct between the Atlantic and Pacific Oceans) republic of Guatamala; and as its site is many miles inland, and the roads such as only to allow the parts being transported thither on mules’ backs, and the load for a mule, including saddle, being from 230 to 240 lbs., it is necessary that no part of the bridge should weigh more than 100 lbs.; and, as the river runs through a mountainous district, and is subject to frequent and very rapid floods, it was also necessary that this bridge should consist of only one arch. This arch is composed of three ribs of wrought iron, forming the segment of a circle; its chord is 83 feet, and rise 7 feet. Each rib is composed of 27 pieces, 3 ft 1¾ inches long; the section of the rib is 10 inches by 1½, with a flange on each side at the 1 inch square. These pieces are made here in two halves for the convenience of transport. The pieces forming the rib are joined together by strong side links, and 3 inch joint bolts [Here a drawing shows two pieces of L section back-to-back].

"The three ribs of the bridge are connected together by cross stays of 2 1/8 round iron, and the whole is strengthened laterally by diagonal bracing fastened to the ends of the cross stays. As it is intended principally for the passage of horses or mules, the breadth is only 9 feet. The roadway is formed of strong planking bolted to the ribs. The side railing (of wood) is also bolted to the ribs by strong iron straps.—The weight of the whole is only 13 tons, and as all the parts are simple and easily made, its cost is very small compared to that of a suspension bridge. The accuracy of the joints, and the strength of the whole have been tested by suspending from the centre a load of three tons.—The appearance of the whole is peculiarly neat and light, and I think it would make a very pretty object crossing any piece of ornamental water, such as the Serpentine in London, or a stream in a gentleman's park, &c.—This bridge may be built without any piers or buttresses, and its several parts may be carried by an army, so as with the utmost expedition to cross rivers too deep to be forded. According to the tests made, its strength is very great, and its durability undoubted.
The reason why the pieces should be no more than 100 lbs. each, is because the mule must be loaded piece being suspended on either side of it." '

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